Apparatus and method for increasing hydraulic capacity of a gravity sewer

ABSTRACT

A method for increasing hydraulic capacity of a gravity sewer system includes installing a receiving structure within or proximate to at least a portion of the gravity sewer system. The receiving structure has at least one fluid inlet opening, at least one liquid outlet opening, and at least one gas outlet opening. The method further includes evacuating at least some of any gas within the receiving structure through the at least one gas outlet opening to create a vacuum within the receiving structure, receiving a flow of at least liquid through the at least one fluid inlet opening of the receiving structure and into the receiving structure, and discharging at least some of the liquid from the receiving structure through the at least one liquid outlet opening of the receiving structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 13/967,672, filed on Aug. 15, 2013, currentlypending, which is a continuation application of InternationalApplication No. PCT/US2012/025561, filed Feb. 17, 2012, which waspublished on Aug. 23, 2012, under International Publication No. WO2012/112838 A1, and which claims the benefit of U.S. Provisional PatentApplication No. 61/463,456, filed Feb. 17, 2011 and entitled “A Systemand Method For Increasing Hydraulic Capacity of an Existing Sewer forUse With Combined Sewer Systems and Sanitary Sewer Systems,” the entirecontents of all of which are incorporated by reference herein.

This application also claims priority to U.S. Provisional PatentApplication No. 61/995,097, filed on Apr. 1, 2014, entitled “Apparatusand Method for Increasing Hydraulic Capacity of a Gravity Sewer,”currently pending, the entire contents of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention is directed generally to an apparatus and methodfor increasing the hydraulic capacity of a sewer system. Moreparticularly, the present invention is directed to a receiving structurepositioned within or proximate to a gravity sewer system for increasingthe hydraulic capacity of the sewer system during a period in which thegravity-flow capacity of the sewer system would otherwise be exceeded.

Combined sewer systems were the “state-of-the-art” during the early 20thcentury. In addition to the collection and transport of municipalwastewater, these combined sewers were designed for stormwater flows aswell—therefore the term “combined.” The design of combined sewer systemsincluded “overflow structures.” When a wet weather event (for example, astorm, heavy rain or snowmelt) created stormwater flows which exceededthe design capacity (i.e., hydraulic capacity) of the combined sewersystem, the excess flow (i.e., the combined sewer overflow “CSO”) wouldbe intentionally diverted to nearby surface water via these overflowstructures.

Later in the 20th century, the “state-of-the-art” shifted to the designand construction of separate sewers—individual sewer systems formunicipal wastewater and stormwater. The design capacity of the sanitarysewer was intended to collect and transport municipal wastewater fromthe service area. Experience has shown that unintended water fromnon-municipal sources (i.e., stormwater) also enters the sanitarysewers. During wet weather events these excessive flows create sanitarysewer overflows (“SSO”) at locations which were not intentionallydesigned to accommodate such overflows.

The current approach taken by the United States Environmental ProtectionAgency (“USEPA”) to deal with the issue of CSO and SSO environmentalimpacts is based on legally-binding “Consent Decree” agreements betweenthe USEPA and the sewer system entity—typically a municipal governmentor agency. The individually-negotiated Consent Decrees include ascope-of-work and schedule intended to reduce the frequency and volumeof CSO during wet weather events.

The scope-of-work includes an assessment and evaluation oftechnically-feasible alternatives. Where increased hydraulic capacity isneeded in order to reduce the frequency and volume of overflows, thetypical alternatives often considered are parallel sewers and/ortunnels. Such alternatives are often very expensive solutions to dealwith short-duration problems created by only a few wet weather eventsannually.

Therefore, it would be desirable to create an apparatus and method thatalleviates or overcomes the above-described disadvantages ofconventional sewer systems. More specifically, it would be desirable tocreate an attachment or addition to gravity sewer systems that—whennecessary or desired—increases the hydraulic capacity of the sewersystem, which is preferably an established or existing gravity sewersystem. The present invention accomplishes the above objectives.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, a preferred embodiment of the present invention providesa system and method for increasing the hydraulic capacity of a gravitysewer. A “receiving structure” of the present invention is constructedat a downstream end of a section of sewer which is in need of additionalcapacity. When the receiving structure is caused to have an internalpressure less than atmospheric pressure, the hydraulic gradient of thesection of sewer is increased; and, thereby its hydraulic capacity canbe increased and controlled.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of preferred embodiments of theinvention will be better understood when read in conjunction with theappended drawings. For the purpose of illustration, there are shown inthe drawings embodiments which are presently preferred. It should beunderstood, however, that the invention is not limited to the precisearrangements and instrumentalities shown.

In the drawings:

FIG. 1 is a schematic view, partially in cross-section, of two sectionsof a gravity sewer with sewer pipe or conduit between adjacent manholes.The first sewer pipe 12 is relatively flat; and, the second sewer pipe16 is relatively steep. At full-flow, the hydraulic gradients (14 a and14 b) are parallel to the slope of each sewer pipe. While normallydepicted above the sewer pipe, in this figure the hydraulic gradient isintentionally shown beneath the sewer pipe in order to more clearlydemonstrate the effect of the present invention.

FIG. 2 is a schematic view, partially in cross-section, of the first andsecond sewer pipes of FIG. 1 plus a receiving structure (10). Also, atleast one vacuum device 26 is connected to gas outlet opening 22 ofreceiving structure 10. While normally depicted above the sewer pipes,in this figure the overall hydraulic gradient 14 c is intentionallyshown beneath the sewer pipes in order to more clearly demonstrate theeffect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “left,” “top,” “up” and down,” andderivatives thereof, designate directions in the drawings to whichreference is made. Unless specifically set forth herein, the terms “a,”“an” and “the” are not limited to one element, but instead should beread as meaning “at least one.” The terminology includes the words notedabove, derivatives thereof and words of similar import.

Referring to the drawings, the first sewer pipe 12 of FIG. 1 has amaximum hydraulic capacity at full flow of a liquid, such as water,which is determined by its size and material-of-construction and itshydraulic gradient 14 a. Likewise, the second sewer pipe 16 of FIG. 1has a maximum hydraulic capacity at full flow of a liquid, such aswater, which is determined by its size and material-of-construction andits hydraulic gradient 14 b. It is preferred that the second sewer pipe16 will have a full-flow hydraulic capacity which is greater than thefirst sewer pipe 12.

Flows in excess of the maximum hydraulic capacity of first sewer pipe 12will back-up and cause overflow conditions upstream (i.e., to the leftin FIG. 1) of first sewer pipe 12.

Referring to the drawings, FIG. 2 shows a downstream end of first sewerpipe 12 of FIG. 1 connected to a receiving structure 10 as is theupstream end of second sewer pipe 16 of FIG. 1. Except for theseconnections and outlet opening 22 to vacuum device 26, the receivingstructure 10 is otherwise preferably a completely enclosed system orcontainer; but, the present invention is not so limited

The air within receiving structure 10 is caused by vacuum device 26 tohave an internal vacuum [the air pressure (“Pair”) is less thanatmospheric pressure]. The equipment and controls for these vacuumwastewater systems are well known by those skilled in the art, andfurther description thereof is not necessary for a full and completeunderstanding of the present invention. Atmospheric pressure at sealevel is approximately 14.7 psi which is approximately equivalent to 34feet w.c. (water column). In other words, for example, a column of water34 feet high would create a pressure of approximately 14.7 psi at thebase of the column.

While a perfect vacuum is impractical for actual operation, if the airwithin receiving structure 10 was eliminated in order to create aperfect vacuum, the hydraulic gradient 14 a at the downstream end offirst sewer pipe 12 in FIG. 1 would be lowered by approximately 34 feet.

In actual practice, the design and operation of the present inventionwill be site-specific and dependent upon creating the increasedhydraulic capacity desired. In actual practice, it will be practical tooperate so that the air pressure within the receiving structure 10 iscaused to be in-the-range-of approximately 6/7 to 3/7 of atmosphericpressure thereby lowering the hydraulic gradient at the downstream endof first sewer pipe 12 by approximately 5-20 feet and therebysubstantially increasing the hydraulic capacity of first sewer pipe 12when compared with its full-flow gravity capacity.

As shown in FIG. 2, at the upstream end of second sewer pipe 16 thehydraulic gradient 14 c is also lowered by the same amount as it is theat the downstream end of first sewer pipe 12. This decreases thehydraulic capacity of the second sewer pipe 16 (when compared to itsfull-flow gravity capacity) while still having a hydraulic capacityequal or exceeding the increased hydraulic capacity of first sewer pipe12. Importantly, the result is to create an overall hydraulic gradient14 c which is greater than the gravity-flow hydraulic gradient 14 a offirst sewer pipe 12 thereby creating a reduction in the frequency ofoverflows upstream of first sewer 12.

Further, in “flat-to-steep” situations such as shown on FIG. 1 and FIG.2, the increased hydraulic capacity in first sewer pipe 12 isaccomplished without a pump or other liquid evacuation device includedamong the apparatus. Avoiding pumps or other liquid evacuation devicesassociated with receiving structure 10 obviates the need for dealingwith (via screens or similar devices) large objects commonly found inthe stormwater component of combined sewer flows. This also eliminatesthe need for additional equipment, operation and maintenancerequirements for redundancy, back-up power, controls, etc, associatedwith such pumps or other liquid evacuation devices.

Another “flat-to-steep” situation can be found in combined sewer systemprojects which include tunnels. Relatively flat consolidation sewersintercept flow at CSO locations and transport flow to (steep) tunneldrop shafts.

It is important to note that a preferred use of the present invention isto temporarily increase the hydraulic capacity of first sewer pipe12—perhaps for only a few hours during each of only a few wet weatherevents per year. Furthermore, the increase in hydraulic capacity ispreferably widely adjustable (by selectively, for example, controllingthe vacuum level in the receiving structure 10) and can be tailored tomatch the conditions created by specific wet weather events when theyoccur. The capital and operating cost savings possible through the useof the present invention are thought to be very significant whencompared to the very expensive alternatives of parallel sewers and/ortunnels for the reduction of CSO and SSO frequency and volume.

As understood by those skilled in the art, an existing first sewer pipe12 and/or an existing second sewer pipe 16 such as constructed yearsago, for example, could be modified, adjusted and/or retrofitted toaccommodate or attach to one or more receiving structures 10, whichcould be in series or in parallel.

Finally, it will be appreciated by those skilled in the art that changescould be made to the embodiments described above without departing fromthe broad invention concept thereof. It is understood, therefore, thatthis invention is not limited to the particular embodiments disclosed,but is intended to cover modifications within the spirit and scope ofthe present invention.

What is claimed is:
 1. A method for increasing hydraulic capacity of agravity sewer system, the method comprising: installing a receivingstructure within or proximate to at least a portion of the gravity sewersystem, the receiving structure having at least one fluid inlet opening,at least one liquid outlet opening, and at least one gas outlet opening;evacuating at least some of any gas within the receiving structurethrough the at least one gas outlet opening to create a vacuum withinthe receiving structure; receiving a flow of at least liquid through theat least one fluid inlet opening of the receiving structure and into thereceiving structure; and discharging at least some of the liquid fromthe receiving structure through the at least one liquid outlet openingof the receiving structure.
 2. An apparatus for increasing hydrauliccapacity of a gravity sewer system, the apparatus comprising: areceiving structure operatively connected to the gravity sewer system,the receiving structure including: at least one fluid inlet openingoperatively connected to an upstream section of the gravity sewersystem; at least one liquid outlet opening operatively connected to adownstream section of the gravity sewer system; and at least one gasoutlet opening; at least one vacuum device operatively connected to theat least one gas outlet opening of the receiving structure; and with noliquid evacuation device operatively connected to the at least oneliquid outlet opening.